Reaction-to-fire performance of fire-retardant treated wooden facades in Japan with respect to accelerated weathering

Wood has been used for building facades to enhance the aesthetic design of buildings since the revision to the evaluation method associated with the amendment of the Building Standard Law of Japan in 2000. In response, wood that has been pressure-impregnated with fire retardants (fire-retardant treated wood) is often used to ensure it is safe in the event of a fire. Currently, when fire-retardant-treated wood is tested for certification of reaction to fire performance, a cone calorimeter test is conducted in Japan. This test applies radiant heat to the surface of a square specimen, 100 mm each side, immediately after it has undergone fire-retardant treatment. However, when applying fire-retardant treatment to wood, aqueous chemical injection is the standard procedure. When wood is actually used to construct a building, there is a concern about environmental forces such as wind and rain that could cause the wood to deteriorate, and concerns about performance degradation associated with aging. One of the past studies in Japan [1] conducted a cone calorimeter test after an outdoor exposure test and accelerated weathering test, compared the post-test performance with the initial performance and confirmed the amount of remaining fire retardant in the treated wood had been reduced. However, no comparison of the fireproof performance of fire-retardant wood in actual use in a building facade had been conducted in Japan. There have been already valuable researches [e.g. 2, 3] on this issue internationally, but this paper is the first step in Japan and authors hope to focus on the wooden façade construction technique and the standard façade test in Japan